Matrix metalloproteinases (MMPs) and aggrecanases (ADAMTS=a disintegrin and metalloproteinase with thrombospondin motif) are a family of structurally related zinc-containing enzymes that have been reported to mediate the breakdown of connective tissue in normal physiological processes such as embryonic development, reproduction, and tissue remodelling. Over-expression of MMPs and aggrecanases or an imbalance between extracellular matrix synthesis and degradation has been suggested as factors in inflammatory, malignant and degenerative disease processes. MMPs and aggrecanases are, therefore, targets for therapeutic inhibitors in several inflammatory, malignant and degenerative diseases such as rheumatoid arthritis, osteoarthritis, osteoporosis, periodontitis, multiple sclerosis, gingivitis, corneal epidermal and gastric ulceration, atherosclerosis, neointimal proliferation (which leads to restenosis and ischemic heart failure) and tumor metastasis.
The ADAMTSs are a group of proteases that are encoded in 19 ADAMTS genes in humans. The ADAMTSs are extracellular, multidomain enzymes whose functions include collagen processing, cleavage of the matrix proteoglycans, inhibition of angiogenesis and blood coagulation homoeostasis (Biochem. J. 2005, 386, 15-27; Arthritis Res. Ther. 2005, 7, 160-169; Curr. Med. Chem. Anti-Inflammatory Anti-Allergy Agents 2005, 4, 251-264).
The mammalian MMP family has been reported to include at least 20 enzymes, (Chem. Rev. 1999, 99, 2735-2776). Collagenase-3 (MMP-13) is among three collagenases that have been identified. Based on identification of domain structures for individual members of the MMP family, it has been determined that the catalytic domain of the MMPs contains two zinc atoms; one of these zinc atoms performs a catalytic function and is coordinated with three histidines contained within the conserved amino acid sequence of the catalytic domain. MMP-13 is over-expressed in rheumatoid arthritis, osteoarthritis, abdominal aortic aneurysm, breast carcinoma, squamous cell carcinomas of the head and neck, and vulvar squamous cell carcinoma. The principal substrates of MMP-13 are fibrillar collagens (types I, II, III) and gelatins, proteoglycans, cytokines and other components of ECM (extracellular matrix).
The activation of the MMPs involves the removal of a propeptide, which features an unpaired cysteine residue complexes the catalytic zinc (II) ion. X-ray crystal structures of the complex between MMP-3 catalytic domain and TIMP-1 and MMP-14 catalytic domain and TIMP-2 also reveal ligation of the catalytic zinc (II) ion by the thiol of a cysteine residue. The difficulty in developing effective MMP inhibiting compounds comprises several factors, including choice of selective versus broad-spectrum MMP inhibitors and rendering such compounds bioavailable via an oral route of administration.
MMP-3 (stromelysin-1; transin-1) is another member of the MMP family (Woesner; FASEB J. 1991; 5:2145-2154). Human MMP-3 was initially isolated from cultured human synoviocytes. It is also expressed by chondrocytes and has been localized in OA cartilage and synovial tissues (Case; Am. J. Pathol. 1989 December; 135(6):1055-64).
MMP-3 is produced by basal keratinocytes in a variety of chronic ulcers. MMP-3 mRNA and Protein were detected in basal keratinocytes adjacent to but distal from the wound edge in what probably represents the sites of proliferating epidermis. MMP-3 may this prevent the epidermis from healing (Saarialho-Kere, J. Clin. Invest. 1994 July; 94(1):79-88)).
MMP-3 serum protein levels are significantly elevated in patients with early and long-term rheumatoid arthritis (Yamanaka; Arthritis Rheum. 2000 April; 43(4):852-8) and in osteoarthritis patients (Bramono; Clin Orthop Relat Res. 2004 November; (428):272-85) as well as in other inflammatory diseases like systemic lupus erythematosis and ankylosing spondylitis (Chen, Rheumatology 2006 April; 45(4):414-20.).
MMP-3 acts on components of the ECM as aggrecan, fibronectin, gelatine, laminin, elastin, fibrillin and others and on collagens of type III, IV, V, VII, KX, X (Bramono; Clin Orthop Relat Res. 2004 November; (428):272-85). On collagens of type II and IX, MMP-3 exhibits telopeptidase activity (Sandell, Arthritis Res. 2001; 3(2):107-13; Eyre, Clin Orthop Relat Res. 2004 October; (427 Suppl):S118-22.). MMP-3 can activate other MMP family members as MMP-1; MMP-7; MMP-8; MMP-9 and MMP-13 (Close, Ann Rheum Dis 2001 November; 60 Suppl 3:iii62-7).
MMP-3 is involved in the regulation of cytokines and chemokines by releasing TGFβ1 from the ECM, activating TNFα, inactivation of IL-1β and release of IGF (Parks, Nat Rev Immunol. 2004 August; 4(8):617-29). A potential role for MMP-3 in the regulation of macrophate infiltration is based on the ability of the enzyme to converse active MCP species into antagonistic peptides (McQuibban, Blood. 2002 Aug. 15; 100(4):1160-7.).